1. Field of the Disclosure
Embodiments disclosed herein generally relate to the transport of bulk materials to and from process locations. More specifically, embodiments disclosed herein relate to methods for transferring granular scavenger material between pressurized containers. More specifically still, embodiments disclosed herein relate to methods for transferring granular H2S scavenger material between pressurized containers as a dense phase. Even more specifically, embodiments disclosed herein relate to methods for transferring both unused and spent granular material between pressurized vessels disposed on land-based facilities, offshore supply vessels, and offshore production platforms.
2. Background Art
Drilling and production of oil or gas wells often requires granular materials to be taken to and removed from drilling and production locations both onshore and offshore. Examples of such granular materials be taken to such locations include fluid additives for drilling and completing a well and hydrogen sulfide treatment material for production of a well. Examples of material removed from drilling locations include dried cuttings and from production locations, spent hydrogen sulfide treatment material.
Some materials tend to be relatively fragile and bulk transport of these materials is often limited to bags so that the material is held in a stable position and does not get crushed to the extent that it would in a bulk container or truck. Due to this limitation, certain materials aren't routinely used offshore because it is difficult logistically to get the material onto an offshore rig. Further, storage on offshore rigs is quite limited and storing bags of material is not practical.
One type of granular material includes, granular hydrogen sulfide (“H2S”) scavenger material, that may be transferred from supply vessels to offshore production vessels, where the granular scavenger material is used to remove H2S from produced gaseous hydrocarbons, such as natural gas or off-gas production fluids. Typically, the transfer of granular H2S scavenger material occurs through the transfer of boxes or bags of dry material to supply vessels via crane lifts, gravity tanks, and conveyor belts. Depending on the volume of granular H2S scavenger material required for a specific operation, the number of crane lifts may be substantial. For example, in a typical operation, several hundred crane lifts may be required to transfer sufficient granular H2S scavenger material from a land-based facility to a boat. Additional crane lifts may be required to transfer material from the boat to the rig, and still more crane lifts may be required to return spent material to shore.
After the scavenger materials are transferred to the offshore location, the scavenger materials may be transferred or pumped to an offshore platform for use in a reactor to remove H2S. In offshore operations, depending on the volume of scavenger required, a supply vessel may have to make several trips, returning to a land-based facility each time, to procure additional granular scavenger material. Each time a supply vessel leaves an offshore platform to procure additional supplies, the drilling/production operation incurs additional expenses including the cost of transporting the granular scavenger material, fuel costs associated with trips to shore, and lost time, as each trip to shore and then back to the drilling and/or production platform may require several days.
In addition to requiring numerous crane lifts and/or vessel transfers, procurement and then transportation of granular H2S scavenger material to and from an offshore platform require time consuming and dangerous operations to clean spent scavenger material from the reactor. The conventional method of cleaning the reactor involves the use of hand tools and manually controlled water lances to break the material out of the vessel. Such operations may require personnel to undertake hazardous work.
Accordingly, there exists a need for methods of transferring scavenger materials to and from drilling rigs, as well as methods and apparatuses for holding bulk granular material so that it may be transferred to or from an offshore location.